A knee-protecting airbag apparatus mounted on a steering column is known from JP 2002-37003. An airbag of this airbag apparatus is housed at a lower region of a space inside a column cover in a folded state. In operation, the airbag is fed with inflation gas and emerges from the column cover to be deployed in front of knees of a driver.
More specifically, when an inflator located inside the airbag discharges inflation gas obliquely downward to the left and right, the airbag unfolds and inflates radially from a substantial center of the column cover, and protects knees of a driver from the column cover in such a manner as to open up the knees. The inflator is secured to a column tube of the steering column while securing a region of the airbag attached to an airbag housing together to the column tube.